Generally satisfactory methods and apparatus are available in known art for preparing, merging and controlling multiple layers of plastic films and the like for processing in one plane into permanent or temporary laminations. However, there appears to be no entirely satisfactory method among those known for merging and controlling multi-layered, temporarily bonded webs in processes requiring radically changing planes and shapes of the moving web such as is experienced in tube-forming in a form-fill-seal bagging machine. Better capability to structure multiple-ply webs, including a scrim ply, as an example, would be extremely desirable for the production of improved industrial size plastic bags, i.e., filled, heavy duty commercial bags of about 25 pounds (11.35 kgs) gross weight or greater.
Accordingly it is the objective of this invention to provide an improved method for preparing heavy duty filled plastic bags possessing improved resistance to severe distortion and damage under typical and characteristic warehouse storage, and transport systems applicable to this class of bags.
It is particularly an objective of this invention to provide such method adapted to economically and reliably prepare scrim reinforced heavy duty bags wherein the scrim material may be reliably structured into the bag and strongly secured in the bag seals to produce an end product having maximum and generally heretofore unachieved strength and dimensional stability in both the hoop and axial directions.
It is yet a further objective of this invention to provide an improved method admirably suited to unwind and combine equal linear quantities of distinctly different plies of material including a scrim ply, wherein the process achieves uniformity of stretch between the various plies, and additionally achieves and maintains excellent edge alignment, to thereby produce and prepare a generally wrinkle-free composite web suited for direct conversion into form, fill and seal industrial size bags.
These and other advantages and cognate benefits of the invention are achieved by the method of preparing filled industrial size bags by the steps comprising: converting a scrim reinforced composite web into a tube having overlapped marginal edges, sealing the marginal edges together securing the scrim in the seal, thereafter periodically filling the tube with product and sealing the tube transversely about each successive product fill securing the scrim also in the transverse seals, and combined therewith, the further steps of preparing the composite web in line with the foregoing steps, and comprising unwinding a carrier ply comprising a plastic film from a wound up supply roll and training the carrier ply about the surface of revolution of a wound up roll of a continuous reinforcing scrim ply, drawing the carrier ply forward and causing it to travel about the surface of revolution of the scrim roll substantially without slippage, thereby tying the carrier ply by frictional surface contact to the scrim ply to provide substantially equal lengths of the scrim and the carrier plies in combined form, and applying a second plastic film to the opposite side of the scrim ply, said process being further characterized by the carrier ply comprising a ply of said filled industrial size bags.